The present invention relates to a method for repairing optical elements having a coating, as well as to optical elements correspondingly prepared therefor and to optical elements repaired by the corresponding method.
For the production of microelectronic components or other micro- or nanostructured elements, lithography methods are used in which light, i.e. electromagnetic radiation in general, with short wavelengths is being used increasingly in order to be able to achieve a corresponding resolution. For example, EUV (extreme ultraviolet) light with wavelengths in the range of 13 nm may be used as electromagnetic radiation. The corresponding projection exposure apparatus have optics which comprise a multiplicity of mirrors. Furthermore a collector, which collects the light from the EUV light source, is provided in such a projection exposure apparatus. In particular, the collector is exposed to high thermal loads and, besides the irradiation due to the EUV light, also possible loads due to particles incident from the light source.
Since the corresponding optical elements, such as mirrors and the collector, of a projection exposure apparatus are manufactured with great cost, it is advantageous to provide opportunities for repair. Correspondingly, for example from JP 06124876 A and US 2002/0063965 A1 (both of which are hereby incorporated into the present application by reference), it is known that optical elements can be refurbished if a cleaving layer is provided between the substrate, i.e. the optical element, and a functional coating on the optical element, for example an antireflection layer or reflection layers, which allows cleaving of the functional coating. The corresponding substrate can therefore be reused by applying a new coating.
Although the cleaving layer is intended to permit simple cleaving of the coating, removal of the coating may cause damage to the surface of the optical element so that the fresh coating does not lead to the desired result and the optical element may possibly need to be rejected.